A grille is a vent that does not have a damper. A register a vent that does have a damper.
A damper is a movable flap or plate that regulates airflow.
A supply grille or register is a vent in which the air is coming out of the wall, ceiling, or floor. It supplies air to the space.
A return grille or register is a vent which takes air from the space and returns it back to the fan or air handler.
Floor grilles or registers can support the weight of a person (extra bracing) while wall ones cannot.
The list size is typically the opening (hole) size. This is the size entered on the ordering page. The actual grille size will be a bit smaller (see grille specifications for details) to allow the grille to slide into the opening.
For most manufacturers you need to remove the existing grille to measure the size of the actual opening (hole). Grilles are sized based on a LIST SIZE which is normally the size of the opening. The grille is then undersized to make sure it fits into the hole and has a flange to cover up the area around the opening. Refer to the information cut sheets for each grille type for their individual measuring requirements.
Yes, but it does take some work. Mill finish grilles may still have surface oils from the manufacturing process. You will have to degrease and prime the grille before painting. Dayus recommends the silver painted grilles if you intend to paint a custom color. The silver will act as a primer layer for your paint.
Sure! If you do not need to adjust the volume of air you can certainly use a grille with no damper. In fact we prefer balancing airflow closer to the furnace/air handler and then using grilles with no damper.